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The Dotson Ice Shelf, which abuts the warm waters of Antarctica’s Amundsen Sea, has exhibited high rates of ocean-driven basal melting in recent decades. As part of the UK-US ITGC collaboration, we surveyed the ice front using a vertical microstructure profiler (VMP) and two ocean gliders equipped with shear and temperature microstructure probes, as well as an ordinary conductivity-temperature sensor. Closely spaced (~1 km horizontal resolution) profiles in the principal in- and outflow regions were collected using the VMP, while the gliders conducted a series of near-zonal sections along the ice front over a three-week period. The glider sections reveal a concentrated inflow, 10 km across, of Circumpolar Deep Water in the east; outflow is concentrated in the west, but occurs over the remainder of the 40 km section. Estimates of turbulent kinetic energy dissipation rate, ε, from shear and temperature, and from gliders and the VMP, generally agree to within an order of magnitude. High values of ε (10-8to 10-7W kg-1) are observed at the sea floor in the inflow region, a result of bottom friction, and throughout the water column in the principal outflow region. In the centre of the section, ε is lower (10-11to 10-10W kg-1), but for a region of elevated ε at the interface between Circumpolar Deep Water and the Winter Water that overlies it. We also calculate horizontal heat transports and, from ε, turbulent vertical heat fluxes, key quantities for understanding the influence of the ocean on basal melting., The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)

Ice shelves terminating towards the Amundsen Sea are losing mass rapidly, exporting an increasing amount of meltwater into the ocean. Investigation into the fate of the glacial meltwater in the Amundsen Sea is therefore pressing for predicting the future climate response to the ice shelf processes. However, observations near ice shelves often lack continuity in either time or space, limiting our knowledge of the meltwater pathway. In summer 2022, we deployed six ocean gliders in front of the Dotson Ice Shelf (DIS), obtaining two ship CTD transects and 573 glider profiles, yielding more than ten fine-resolution (median horizontal sampling interval: 650 m) glider transects along the DIS within three weeks, allowing us to compare the full picture along DIS over short time scales (median sampling interval: 4.5 days). Glider transects reveal that the meltwater content is higher (about 20 g/kg) in the west (outflow) and lower in the east (inflow), with a meltwater-poor layer centred at about 350 m sandwiched by two meltwater-rich layers (above about 250 m and centred at about 450 m). We find particularly meltwater-poor cores within the meltwater-poor layer, potentially indicating eddies. Isopycnals diverge near the meltwater outflow core and shoal below about 600 m at the inflow region, indicating geostrophic flow out of and into the cavity respectively. We calculate the volume transport of meltwater exported from the ice shelf cavity and assess its variability during the three weeks., The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)

Quantifying the heat absorbed and released by the ocean is important in understanding the role of air-sea interactions in global climate. Estimates from reanalysis products are readily available but high-resolution (both temporal and spatial) observations are much less so. To investigate ocean heat budget and air-sea interactions on a local scale, we deployed four autonomous platforms east of Barbados as part of the Eurec4a campaign, January- February 2020, in a 10 km x 10 km region. 3 Seagliders undertook 581 dives yielding 1162 vertical ocean profiles, and our 5 m wave-powered surface vessel, Caravela, travelled more than 1000 km over ground. Variations in the surface mixed layer properties are described by Seaglider profiles of temperature and salinity. For example, the mixed layer depth varies over days to weeks between 11 m and 45 m. Turbulent microstructure from one Seaglider estimates the contribution of vertical mixing to the heat budget. Variations in upper ocean heat content are derived, and we test the extent to which local air-sea fluxes can account for changes in heat content. These fluxes are derived from Caravela’s in-situ measurements, including downwelling long-wave and short-wave radiation (long-wave observations varying from 370 W/m² to 490 W/m², with a peak solar radiation of 1440 W/m²), supplemented by fluxes from the ERA5 reanalysis. We also observe the diurnal cycle of the upper ocean heat content. In this presentation, we discuss the potential of these surface and subsurface platforms to derive an observationally-based heat budget on a local scale., The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)

This discussion paper explains how the UK’s climate is linked to conditions in the Arctic, and why a UK Arctic science strategy is integral to understanding how global warming will change the Arctic and affect the UK.